The former SIDM (Serial Impact Dot Matrix) print head (clapper type) (hereinafter: print head) is composed of a plurality of printing element, and it is to explain the structure on the basis of FIG. 10 and FIG. 11.
With respect to FIG. 10, a coil 106 is rolled in an arbitrary turn number around a coil bobbin 102, and a columnar core 101 with a good magnetic property is furnished in the inside. A core yoke 103, a space yoke 125 and a space sheet 126 are furnished by touching the core 101, further, an armature 104 is furnished to face the core 101 across a gap, furthermore, an armature yoke 116 is furnished by touching the space yoke 125 across the armature 104, and these magnetic materials form a magnetic path 121.
The armature 104 is composed of compression spring and the like, is pressed to a limiter portion 107 through a reset spring 108 whose one end is fixed, and a wire 105 is welded to the tip. As shown by FIG. 11, one sheet or a plurality of sheets of spacer 13 is mounted between the limiter portion 107 (rubber limiter 107a and sheet limiter 107b) and a housing 117, thus, by moving a position of the touching surface of the limiter portion 107 with the armature 104 up and down, a wire stroke of armature 104 is adjusted.
The wire 105 as respective printing elements is positioned through a wire guide 109 fixed in a guide nose 120 so that the tip forms a dot matrix, and a plurality of guides 118 fixed in the guide nose 120 suppress horizontal vibration and buckling of the wire 105.
The reset spring 108 stated above is furnished in a holder spring 124, and makes a pressing force act on the armature 104 to return to a standby position. Further, as shown by FIG. 11, the armature 104 is pressed by a pressure spring 115 to the space yoke 125 surface and the armature yoke 116 surface through the touched space sheet 126, and the touched point becomes a rotation fulcrum 129 around which the armature 104 moves. The pressure spring 115 is fixed on a surface that is formed by the housing 117, and is bent to an arbitrary angle so that the pressing force acts on a fulcrum portion of the armature 104.
After electric power is supplied from an electric source 112 to the coil 106 through a connector 123 on a head substrate 122, magnetic flux is generated in the magnetic path 121, the magnetic flux of the gap between the core 101 that is a part of the magnetic path 121 and the armature 104 acts as attracting force (electromagnetic force) to attract the armature 104 to the core 101 side.
Thus, the wire 105 joined with the armature 104 starts a motion to the direction of a platen 114, impacts on a paper 111 whose back is supported by the platen 114 through an ink ribbon 110, and forms a dot.
After supply of the electric power from the electric source 112 to the coil 106 is stopped, the attracting force is reduced, and when reaction force of the impact and the pressing force of the reset spring 108 to the armature 104 excel the influence of the attracting force, the armature 104 reverses the direction of the motion, and returns to the position of the limiter portion 107. The limiter portion 107 consists of vibration-damping materials or its composite material, and suppresses the remaining vibration of the armature in reset time so that any problem is not caused on responsiveness in the case that dots are formed continuously.
By controlling the series of operation timing through a controlling section 113, it becomes possible to form a character that is an aggregate of dots on the paper 111. Moreover, a clamp spring 119 is a member for making these parts a unit.
The former print head is composed like this.
Further, there is a print head in which a metal reinforcing plate is furnished between a lever holder for holding a lever (armature) and a fixing spring for fastening and holding a head structure member (for example, referring to patent document 1).
Patent document 1: Japan Utility Model Publication of No. 02-133345 (Page 1, FIG. 1)
However, in the former technology stated above, because the shape of the pressure spring that presses the rotation fulcrum of the armature is limited, there is a problem that it is difficult to obtain enough pressing force to completely prevent a lift of the rotation fulcrum of the armature.
The reason why the shape of the pressure spring is limited as stated above is that, because of mounting of the print head, it is difficult to strengthen the pressing force by broadening width through serving petal shaped leaf spring parts as cantilevers respectively. Further, when the pressing force is strengthened by increasing the plate thickness, it enters into a plastic range, and in the case that the irregular load is added, an appropriate pressing force cannot be assigned because the transformed shape does not return to the original one, and it causes the occurrence of the decline of the motion characteristics and the unevenness among the wire.